US3696244A

US3696244A - Power operated railway switch machine control circuit

Info

Publication number: US3696244A
Application number: US76719A
Authority: US
Inventors: David H Hamley; Lyle L Hylen
Original assignee: Westinghouse Air Brake Co
Current assignee: Hitachi Rail STS USA Inc
Priority date: 1970-09-30
Filing date: 1970-09-30
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03
Also published as: CA943662A

Abstract

This disclosure relates to an electric motor control circuit for electrically power operated trailable railway switches for use in classification yards. The motor control circuit includes normal and reverse control relays which receive and store the command signals. The normal and reverse relays are adapted to energize a motor reversing contactor having a pair of interlocked relays. The interlocked relays include a plurality of bar type contacts which are adapted to energize an electromagnetic clutch and an electric motor for driving the switch points to their extreme positions. An overload device and manual cutout switch are arranged to deactivate the motor control circuit during a motor overload condition and during manual manipulation of the railway switch.

Description

United States atent [4 1 Oct. 3, 1972 Hamley et al.

[54] POWER OPERATED RAILWAY SWITCH MACHINE CONTROL CIRCUIT [72] Inventors: David H. Hamley, Edgewood; Lyle L. I-Iylen, Wilkinsburg, both of Pa.

[73] Assignee: Westinghouse Air Brake Company,

Swissvale, Pa.

[22] Filed: Sept. 30, 1970 [21] Appl. No.: 76,719

[52] US. Cl ..246/242 [51] Int. Cl. ..B61l 5/00 [58] Field of Search ..246/240, 242, 393, 411

[56] References Cited UNITED STATES PATENTS 3,557,364 1/197l Swanton ..246/240 3,522,427 8/1970 Mine ..246/240 2,117,323 5/1938 Hines ..246/242 R Primary Examiner-James B. Marbert Assistant Examiner-George H. Libman Attorney-H. A. Williamson, A. G. Williamson, Jr. and J. B. Sotak [57] ABSTRACT This disclosure relates to an electric motor control circuit for electrically power operated trailable railway switches for use in classification yards. The motor control circuit includes normal and reverse control relays which receive and store the command signals. The normal and reverse relays are adapted to energize a motor reversing contactor having a pair of interlocked relays. The interlocked relays include a plurality of bar type contacts which are adapted to energize an electromagnetic clutch and an electric motor for driving the switch points to their extreme positions. An overload device and manual cutout switch are arranged to deactivate the motor control circuit during a motor overload condition and during manual manipulation of the railway switch.

9 Claims, 1 Drawing Figure POWER OPERATED RAILWAY SWITCH MACHINE CONTROL CIRCUIT machine.

lt is conventional, for example, in railway classification yard operations, to establish various or alternate routes for railway vehicles so that railway vehicles may be assembled on different class tracks in accordance with the train manifest. In an automatic classification yard, the establishment of the route is controlled by a yardmaster or by a computer which remotely controls a power operated railway switch. Generally the railway switch is power operated by an electric motor which moves the switch point between two extreme positions. ln addition, it is desirable to provide a method for manually manipulating the railway switch machine during power failures or during maintenance periods. Thus, a hand throw lever is generally provided for manually throwing the switching points between their two extreme positions. However, it will be appreciated that precautionary measures must be'taken to ensure that the switch machine can not be power operated during manual operation of the switch points in order to ensure that a maintainer or switchman is not exposed to the danger of being injured by a swinging hand throw lever. It is also advantageous to employ a trailable type of switch machine in yard applications in order to avoid undue delays and the accompanying high cost of repairing or replacing a damaged switch. Thus, provisions must be made to protect the switch machine against damage when the switch points are being simultaneously trailed and power operated from a remote location.

In the past, the control circuit which controlled the switch mechanism and the track circuit which determined occupancy of the railway switch track were cooperatively associated in such a manner that allowed misrouting of railway vehicles. Previously, if a vehicle entered and occupied the track section of the railway switch during the power operating cycle, the switch mechanism could shift the switch points to the opposite position or, in some cases, could return the switch points to their original position. That is, in previous railway switches, the switch mechanism returned the switch points to their original position if the track section became occupied before the mid-stroke position was reached. Thus, there is theoretically a 50-50 chance that the railway cars would be misrouted which would therefore require withdrawal and reclassification. It will be appreciated that such operation not only is undesirable but also is costly and time consuming.

Accordingly, it is an object of our invention to provide a new and improved electric motor control system for a railway switch machine.

Another object of our invention is to provide a remotely controlled railway switch having memory for storing the command signals so that the switch points are moved to the extreme position directed by the last command signal.

A further object of our invention is to provide an electric railway switch machine having a reversible motor which is energized to move the switch points between their extreme positions in response to command signals received by the control circuit.

Still another object of our invention is to provide an electric motor control system for a railway switch machine having a normal and reverse control circuit for controlling the energization of a polyphase induction motor.

Still a further object of our invention is to provide a railway switch machine having an electric motor for driving the switch points between their extreme positions and having an overload device for sensing the amount of current flowing through the electric motor and deenergizing the electric motor during an overload condition.

Yet another object of our invention is to provide an improved electric railway switch machine having a cutout switch connected to the control circuit for deactivating the electric motor during manual manipulation of the railway switch.

Yet a further object of our invention is to provide an improved railway switch arrangement having a remotely controllable normal and reverse control circuit for energizing a reversible motor and electromagnetic clutch for shifting the switch points between two extreme positions.

Still yet another object of our invention is to provide a trailable railway switch having a control circuit which stores a received command signal and causes the electric motor to drive the switch points to the desired extreme position.

Still yet a further object of our invention is to provide a new and improved railway switch motor control system which is economical in cost, reliable in operation, durable in use and efficient in service.

Briefly, in accordance with the present invention we provide a unique motor control circuit arrangement for an electrical railway switch machine which moves the switch points between their normal and reverse positions. The circuit arrangement includes a three-phase reversible motor, an electromagnetic clutch and a source of electrical power. A control circuit is selectively controlled from a remote location to cause energization of the reversible motor and the electromagnetic clutch from the power source. The control circuit includes a normal control circuit having a normal control relay which stores a normal command signal and energizes a normally in relay of a mechanically interlocked motor reversing contactor. The energization of the normally in relay closes a first group of contacts which energizes the electromagnetic clutch and the reversible motor so that the switch points are moved to their normal position. The control circuit also includes a reverse control circuit having a reverse control relay which stores a reverse command signal and energizes a reverse out relay of the mechanically interlocked motor reversing contactor. The energization of reverse out relay closes a second group of contacts which energizes the electromagnetic clutch and the reversible motor so that the switch points are moved to their reverse position. A manual cutout switch is common to both the normal and the reverse control circuit to prevent energization of the reversible motor and electromagnetic clutch during manual manipulation of the switch points. An overload relay senses the amount of current flowing through the motor and interrupts the control circuits which in turn deenergizes the reversible motor and the electromagnetic clutch when an abnormal amount of current flows through the reversible motor. A track detector circuit includes a relay having a pair of front contacts common to the normal and reverse control relays for preventing the switch machine from being remotely controlled during occupancy of the switch track section. The normal and reverse control relays include stick circuits which store the command signals and ensure that the switch points will be moved to the desired position when the switch track section becomes occupied after the reception of a command signal.

We shall describe one preferred form of a unique circuit arrangement embodying our invention and shall then point out the novel features and advantages thereof in the claims.

The above objects and other attendant features and advantages of our invention will become more fully evident from the following detailed description when considered in connection with the accompanying drawing.

The single accompanying drawing is a diagrammatic view of a motor control system embodying our invention for an electrically operated railway switch machine.

Referring now to the single FIGURE of the drawing, the reference character SW designates the railway switch comprising two stock or fixed rails 1 and 2 along with two movable switch points 3 and 4. The switch points 3 and 4 are interconnected by a head rod 5 which is secured near the extreme ends of the switch points 3 and 4. As shown, the rails are insulated at points to define the usual track circuit associated with the railway switch by insulating joint 6. As is conventional, the detector track circuit includes a battery 7 and a detector track relay TR, the purpose of which will be described hereinafter. The switch points 3 and 4 are interconnected with a switch machine or operating mechanism and are moved between their normal and reverse positions by means ofa throw rod which is illustrated by the dashed line 8. The switch machine may be of the type shown and disclosed in the copending application for Letters Patent of the United States, Ser. No. 57,571 filed July 23, l970 by Lyle L. Hylen, for A Trailable Railway Switch Machine which is assigned to the same assignee as the present application. In viewing the drawing, the switch machine is disposed on the right-hand side of the track so that the railway switch is a right-hand layout with the right switch point closed. With such a switch layout, the operating rod is in" when the switch points are normal and the operating rod is out when the switch points are reverse. Thus, the term in is synonymous to the term normal while the term out is synonymous to the term reverse in the ensuing discussion. However, it is understood the terms are interchangeable depending upon the railway switch layout. As shown, the switch machine includes a suitable high speed electric motor M having its armature A mechanically coupled to an electromagnetic clutch C through a speed reduction gear train or the like, illustrated by the dashed line 9.

The motor M is preferably but not necessarily a multiple voltage type of polyphase a. c. induction motor having a rating of approximately 1 horsepower. As shown, the induction motor M includes three pairs of field windings F1, F2, and F3 with each pair connected in series relationship for 460 volt operation. The field windings each have one end connected to a common point to form a WYE configuration. The other ends of the field windings F1, F2, and F3 are connected through suitable leads and electrical contacts to a conventional source of a three-phase, 460 volt, 60 hertz, power supply having terminal BX, CX and NX, as will be described in greater detail hereinafter.

As previously mentioned, railway switch machines for usage in classification yard applications are generally remotely controlled from the yardmaster tower which is generally some distance from the switch location. Thus, the above mentioned detector track circuit including relay TR and its front contacts a and b are employed to monitor the condition of the switch track section. It will be noted that when the track section is unoccupied, the track relay TR is energized by battery 7 so that its front contacts a and b are normally closed. However, when the switch track section becomes occupied, the wheels of the vehicle shunt the battery source 7 so that the track relay TR becomes deenergized and the front contacts a and I) become opened. This ensures that a power switching operation may not be instituted after the track section becomes occupied by a railway vehicle.

The front contacts a and b of track relay TR are connected by

leads

11 and 12 to a control selector switch such as, a single-pole double-throw electrical switch having a normal position N and a reverse position R. As previously mentioned, the selector switch 13 may be operated either automatically or manually from a remote location, such as from the yardmasters tower. The selector switch 13 is connected by hot lead 14 to terminal BX of the a. c. power supply. A pair of conductive leads l5 and 16 interconnect the front contacts a and b of track relay TR to one end of the coils of normal control relay NCR and reverse control relay RCR, respectively. The other end of each of the coils of relays NCR and RCR is connected in common by lead 17 which, in turn, is connected to a first manual cut-out switch contact CO1 which is cooperatively associated with the hand throw lever of the switch machine, as shown and described in more detail in the above noted application, Ser. No. 57,57l. The contact CO1 of the cut-out switch is normally closed except during manual operation at which time the switchman or maintainer deactivates power operating mode by opening the manual cut-out switch. Thus, when the contact CO1 is closed, the other ends of the relays NCR and RCR are connected by lead 18 to the terminal NX of the a. c. power supply. Thus, the control relays NCR and RCR are connected in multiple through their respective circuits between terminals BX and NX of the a. c. power supply.

The control relays NCR and RCR include a plurality of front and back contacts which establish the normal and reverse control circuits for controlling the nonnal operation of the railway switch or the reverse operation of the railway switch. The normal control relay NCR includes a stick circuit which ensures that once a normal command signal is initiated the switch machine will drive the switch points to their normal position even though the energizing circuit for the normal control relay is subsequently interrupted by opening of front contact a of track relay TR due to occupancy of the switch section by a railway vehicle. Thus the command signal is effectively stored or held in memory until such time as it is deemed appropriate to deenergize the normal control relay by interrupting its stick circuit. Such operation ensures that the switch points will be moved to their opposite position so that misrouting of the railway vehicles will not occur, as was the case in previous switch arrangements. The normal control relay stick circuit includes lead 20 which has one end connected to lead and has the other end connected to front contact a of the normal control relay NCR. The front contact a of the normal control relay NCR is connected via lead 21 to the back contact 0 of the reverse control relay RCR. The back contact 0 of relay RCR is connected via lead 22 to a limit switch contact AC1 which is normally opened when the switch machine is in its normal position, as shown. The limit switch contact AC] is connected via leads 23,24,25, and 26 to the terminal BX of the a. c. supply source. A second manual cut-out contact CO2 of the motor switch is connected via lead 23 to the lead 24.

A motor reversing contactor MRC includes a normal in" relay MR and a reverse out relay ROR. Each of these relays includes a plurality of front bar type contacts which control the energization of the field windings F1, F2, and F3 of the motor M, as will be described hereinafter. The cut-out contact CO2 is electrically connected via lead 27 to limit switch contact AC2 which is also normally opened when the switch machine is in its normal position, as shown. The limit contacts AC1 and AC2 are controlled by the operating rod 8 which opens and closes the contacts in accordance with the stroke position of the railway switch machine. in actual practice, the limit switch contacts AC1 and AC2 remain closed for the major portion of the switch movement and only are opened when the switch point 3 is approximately three-eighths of an inch from the stock rail 1. As shown, the limit switch contact AC2 is connected via lead 28 to the front contact b of the normal control relay NCR. The back contact b of I the relay NCR is in turn connected via lead 29 to the normally in relay NIR of the motor reversing contactor MRC. As shown, the motor reversing contactor includes a mechanical interlock so that is is not possible to energize both the normal in relay NIR and the reverse out relay at the same time. The normally in relay NIR is connected via lead 30 to the back contact a of an overload relay OR which senses the current flowing through the field windings of the motor M, as will be described presently. The back contact a of overload relay OR is connected via lead 31 to the lead 18 which in turn is connected to the terminal NX of the a. 0. power supply.

Like the normal control relay NOR, the reverse control relay RCR includes a stick circuit which ensures that once a normal command signal is initiated, the switch machine will drive the switch points to their reverse position even though the energizing circuit for the reverse control relay is subsequently interrupted by the opening of the front contact b of the track relay TR due to its release by the occupancy of the switch section by the railway vehicle. As previously mentioned,

I such an operation ensures that once a command signal is received from the computer or yardmaster, the switch mechanism will ensure that the switch points move to the desired position so that an oncoming vehicle is not misrouted to the wrong class track. The stick circuit of the reverse control relay RCR includes lead 33 having one end connected to lead 16 and the other end connected to the front contact a of relay RCR. The front contact a of relay RCR is connected via lead 34 to the back contact 0 of normal control relay NCR, via lead 35 through a limit switch contact AC3. The limit switch contact AC3 is connected via lead 36 to lead 25 which in turn is connected to lead 26. Lead 26 in turn is connected to the terminal BX of the a. c. power supply.

It will be noted that the reverse out relay ROR of the motor reversing contactor MRC is provided with an energizing circuit extending from terminal BX, over leads 26, 25, 24, and 23, through cut-out contact CO2, over leads 27 and 37, through limit switch contact AC4, through front contact b of relay RCR, over lead 39, to relay ROR over lead 30 through contact a of relay OR, over leads 31 and 18 to the terminal NX of the ac. power supply.

As shown, the normal in relay NIR and the reverse out relay ROR of the motor reversing contactor control a plurality of 'bar type contacts which are employed to selectively control the energizing circuits for the induction motor M and for the electromagnetic clutch C. It will be seen that each of the relays of the motor reversing contactor MRC controls four sets of contacts, namely, contact bars a', b, c, and d. As shown, the contact bar a of relay NIR is connected in multiple with contact bar a of relay ROR and their contacts b are also connected in multiple with each other. The contact bar c of relay NIR is connected in common with contact d of relay ROR via lead 43 and contact 0 of relay NIR is connected in common with contact d of relay ROR via lead 44. Thus, the electromagnetic clutch C may be energized either by closure of contact a of relay NIR or by closure of contact a of relay ROR. Thus, the energizing circuit of the electromagnetic clutch C extends from terminal BX, over leads 26, 25, 46 and 47, either through contact a of relay NIR, over lead 42 or through contact a of relay ROR, over lead 48, to one a. c. input terminal of a bridge rectifier BR which converts the alternating current into direct current. As shown, the bridge rectifier BR includes a plurality of diodes D1, D2, D3, and D4 which are conventionally poled to provide a positive and a negative output terminal. Lead 50 interconnects one input terminal of the electromagnetic clutch C to the positive rectifier terminal while lead 51 interconnects the other input terminal of the electromagnetic clutch C to the negative rectifier terminal. A conductive lead 52 is connected to the other a. c. output terminal to the lead 17 which, in turn, is connected through contact CO1 and lead 18 to the terminal NX of the a. c. power supply.

The field winding F1 of the motor M is connected to contact bar b of relay ROR by lead 53, which in turn is connected to contact bar b of relay NIR by lead 43. A common lead 54 interconnects both of the contact bars b of relays ROR and NIR. Lead 54 is connected via lead 55 to lead 26 which in turn is connected to the terminal BX of the a. c. power supply. A lead 56 is connected from field winding F2 to the contact bar of relay ROR. Lead 44 also interconnects lead 56 to the contact bar d of relay NIR. Thus, the field winding F2 may be alternately energized by closure of either contact c of relay ROR or contact d of relay NIR. Contact 0 of relay ROR is connected via leads 57 and 58 to terminal CX of the a. 0. power supply while contact a of relay NIR is connected by

leads

59 and 60, through thermal over load relay OR, and by lead 61 to the terminal NX of the a. c. power supply. The field winding F3 of the motor M is connected by lead 62 to the contact bar d of relay ROR. Lead 62 is also connected to contact bar d of relay NlR by lead 45. Thus, like field winding F2, the field winding F3 may be alternately energized by being either connected to terminal CX and terminal NX of the a. c. power supply by the closing of contact c of relay ROR or the closing of contact d of relay NIR, respectively. Thus, when either of the relays of the motor reversing contactor MRC is energized, the contacts establish energization paths for the electromagnetic clutch C and the field windings of the motor M.

Let us now assume that all the necessary adjustments have been made and the railway switch is functioning properly, so that we may discuss the operation of the railway switch. Let us further assume that switch points are in their normal position, as shown, that the switch section is unoccupied and that the motor control circuit and the associated circuit elements are in the positions as shown in the drawing. Under this condition, the energizing circuits for the motor M, the electromagnetic clutch C, the relays of motor reversing contactor MRC and the stick circuits for the normal and reversing relays NCR and RCR are incomplete due to an open contact in their respective circuits. The detector track circuit is energized so that track relay TR is picked up and its front contacts a and b are closed. The normal control relay NCR is energized through the circuit extending from terminal BX through lead 14 over contact N of the selector switch 13, through lead 11 over front contact a of track relay TR, through lead 15, through relay NCR, through lead 17, over cut-out contact CO1, through lead 18 to the terminal NX. If an approaching vehicle is to be routed to another class track, the switch points must be shifted to their reverse position. To shift the switch points to their reverse position, it is simply necessary to throw the selector switch 13 to its opposite position so that the normal contact N is opened and the contact R is closed. The opening of normal contact N deenergizes the normal control relay NCR while the closing of the reverse contact R establishes an energization path for the reverse control relay RCR through a circuit extending from terminal BX, through leads 14 and 12, over front contact b of relay TR, through lead 16, through relay NCR, through lead 17, over cut-out contact CO1, through lead 18 to the terminal NX of the a. 0. power supply. The deenergization of the normal control relay NCR causes its front contacts a and b to become opened while its back contact 0 becomes closed. When the reverse control relay RCR becomes energized, its front contacts a and b become closed while its back contact 0 becomes opened. The closing of front contact 0 establishes the stick circuit for the reverse control relay RCR which extends from terminal BX, through leads 26, 25, and

36, over limit contact AC3, through lead 35, over back contact c of relay NCR, through lead 34, over from contact a of relay RCR, through relay RCR, through lead 17, over cut-out contact CO1, through lead 18 to terminal NX of the a. c. power supply. As previously mentioned the stick circuit effectively stores the reverse command signal and ensures that the switch machine will move to its reverse position irrespective of the subsequent occupancy of the switch track section by an oncoming vehicle. That is, if the track section becomes occupied after reception of the reverse command signal, the release of the track relay TR and the opening of its front contact b will not cause deenergization of the reverse control relay RCR since it will remain energized over its own stick circuit. The closing of front contact 12 of relay RCR establishes an energizing circuit for reverse out relay ROR. The relay ROR is energized by a circuit extending from terminal BX through leads 26, 25, 24, and 23, over cut-out contact CO2, through leads 27 and 37 over limit contact AC4, through lead 38, over front contact b of relay RCR, through lead 39, through relay ROR, through lead 30, over back contact a of relay OR, through leads 31 and 18 to the terminal NX of the a. c. power supply. The energization of the reverse out relay ROR causes the contacts a, b,c, and a to become closed. The closing of contact bar a of relay ROR establishes an energizing circuit for the electromagnetic clutch C. The clutch C is energized by a circuit extending from terminal BX, through leads 26, 25, 46, 47, over contact bar a of relay ROR, through leads 41 and 48, to one a. c. input terminal of the bridge rectifier BR, and then from its positive d. 0. terminal, through lead 50, through the electromagnetic clutch C through lead 51, to the negative d. c. terminal of the bridge rectifier BR, from the other a. c. input terminal of the a. 0. bridge rectifier BR, through lead 52 and over cut-out contact CO1, through lead 18 to the terminal NX of the a. c. power supply. The closing of contact bars b, c, and d establishes an energizing path for the field windings F1, F2, and F3 of the motor M from the three-phase a. c. power supply. In the instant case field winding F1 is connected over contact b of relay ROR to terminal BX, while field windings F2 and F3 are connected over contacts b and c of relay ROR to terminals CX and NX, respectively. Thus, the motor M becomes energized and the rotation movement of its armature A is coupled through the gear train 9 to the electromagnetic clutch C which moves operating rod 8 and, in turn, drives the switch points 3 and 4 to their reverse position. If no obstruction is blocking the switch points, the various circuit will remain energized until the switch point 4 is approximately three-eighths of an inch from the stock rail 2. When the switch point 4 reaches this position, the operating rod 8 causes the limit switch contacts AC3 and AC4 to become opened so that the stick circuit of the reverse control relay RCR and the energizing circuit of the reverse out relay ROR are interrupted. The deenergization of the reverse out relay ROR causes the contact bars a, b, c, and d to become opened so that the motor M and the electromagnetic clutch C become deenergized. The switch points 3 and 4 are moved the remaining distance of travel by the momentum imparted to the switch mechanism and by the spring assembly as described in detail in the above mentioned application Ser. No. 57,571. Thus, the actuation of the selector switch 13 causes the switch points to be rapidly and positively moved to their reverse position.

Now if it is desired to return the switch points to their normal position, it is simply necessary to flip the selector switch 13 to is opposite position so that its reverse contact R becomes opened and its normal contact N becomes closed. The opening of the reverse contact R deenergizes the reverse control relay ROR by interrupting its energizing circuit. The closing of normal contact N causes energization of the normal control relay NCR which, in turn, energizes the normal in relay NlR over the front contact b of relay NCR. The energization of the normal in relay NlR now causes its contact bars a, b, c, and d to become closed so that the electromagnetic clutch C and the motor M become energized over the alternate energizing paths, as previously described. It will be appreciated that a phase reversal occurs in field windings F2 and F3 so that the armature A rotates in the opposite direction and causes the operating rodS to move the switch points toward their normal position. That is, the field winding F2 is connected to terminal NX over contact d of relay MR and field winding F3 is=connected to terminal CX of contact of relay NlR. Now when the switch point 4 moves approximately three-eighths of an inch away from the stock rail 1, the limit contacts AC3 and AC4 become closed and remain closed so that it is possible to return the switch points to their reverse position if an obstruction is incurred during their movement to their normal position.

When an obstruction is incurred during. either reverse or normal switching operation, the motor will continue rotation but the electromagnetic clutch C will slip so that no damage will occur to the operating rod, the switch points or the switch mechanism. However, if it is recognized that the switch points have incurred an obstruction, the switch points may be returned to their original position either manually or automatically prior to the opening of back contact a of relay OR. If the switch points are not immediately returned to their original position, continued rotation of the motor causes increased current to be drawn by the field windings so that the thermal overload relay OR will become heated and will eventually open its back contact a which deenergizes the normal in relay NIR which, in turn, deenergizes the electromagnetic clutch C and the motor M. After a predetermined time, the overload relay will cool sufficiently to again close its from contact a so that the switch points can be returned to their reverse position. If no obstruction is present the switch points will continue to be power driven to their normal position. When the switch point 3 is approximately three-eighths of an inch from the stock rail 1, the operating rod 8 will open limit switch contacts AC1 and AC2 so that the stick circuit of relay NCR and the energizing circuit of relay NIR will be interrupted and the motor M and clutch C will be energized. The switch points are moved the remaining distance by the inertia and spring action, as mentioned above.

Let us assume that the railway switch is in its normal position as shown and that a maintainer or brakeman desires to manually move the switch points to their reverse position. In order to prevent the possibility of injury to the individual, it is required that the switch mechanism be electrically deactivated so that power operation can not be instituted during manual operation. To accomplish this cut-out contacts CO1 and CO2 are cooperatively associated with the manual hand throw lever of the switch mechanism.

It will be appreciated that the cut-out contacts CO1 and CO2 are operated jointly or in union so that both the normal control relay and the normal in relay circuits and both the reverse control relay and reverse out relay circuits are interrupted when the hand throw lever is being manipulated. Thus, it is impossible to power operate the switch mechanism during manual manipulation of the switch points.

From the foregoing, it will be seen that the presently described railway switch motor control circuit provides a more efficient arrangement for moving the switch points between their two extreme positions. Further, while our invention has been described in regard to a preferred embodiment, it is readily understood that various changes may be made by those skilled in the art without departing from the spirit and scope of our invention. For example, while the invention has been described in regard to a three-phase induction motor, it will be appreciated that a split phase of d.c. type of motor may be employed with equal success. ln addition, it is understood that other types of relays and motor contactors may be employed in practicing our invention and therefore, it is understood that the foregoing description is only illustrative of our invention and is not intended to conventionally limit thereto. Accordingly, it is understood that the invention is not limited to the specific features herein set forth but should be given the breadth as set forth by the terms of the appended claims.

Having thus described our invention, what we claim is:

1. An electric motor control system for a railway switch machine which shifts the switch points between two extreme positions comprising, a reversible motor, an electromagnetic clutch and a source of electrical power, a control circuit including a normal and a reverse circuit for remotely controlling the energization of said reversible motor and said electromagnetic clutch from said power source, said control circuit having a first means for receiving and storing a first command signal, said first means controlling energization of said electromagnetic clutch and said reversible motor so that said switch points are shifted from one to the other extreme position, said control circuit having a second means for receiving and storing a second command signal, said second means controlling the energization of said electromagnetic clutch and said reversible motor so that the switch points are shifted from the other to the one extreme position, said electromagnetic clutch is arranged to slip when the trailing action opposes the shifting of the switch points by the energization of the reversible motor so that no damage will occur to the railway switch, a cut-out switch common to said first and second means for disabling said normal and reverse circuits thereby preventing energization of said reversible motor and said electromagnetic clutch, and an overload device for sensing the amount of cur rent flowing through said reversible motor and for interrupting both said first and second means which causes said reversible motor to be deenergized when an abnormal amount of current flows through said reversible motor.

2. An electric motor control system as defined in claim 1, wherein said reversible motor is a polyphase a. c. induction motor.

3. An electric motor control system as defined in claim 1, wherein a motor reversing contactor includes a plurality of electrical contacts which electrically interconnect said reversible motor to said power source for causing it to move in one or the other direction.

4. An electric motor control system as defined in claim 1, wherein a diode rectifier is connected to said power source for supplying d. c. voltage to said electromagnetic clutch.

5. An electric motor control system as defined in claim 1, wherein an electromagnetic relay having a front and a back contact is coupled to said first and second means for providing a stick circuit for each relay so that the switch points are moved to the extreme position directed by the last command signal.

6. An electric motor control system as defined in claim 1, wherein limit contacts interrupt said normal and reverse circuit as the switch points approach the one or the other extreme position.

7. An electric motor control system as defined in claim 4, wherein said motor reversing contactor includes a pair of windings which are interlocked to prevent simultaneous energization of both windings.

8. An electric motor control system as defined in claim 1, wherein a detector track circuit associated with the track switch operated by the railway switch machine for disabling said control circuit during the occupancy of said detector track circuit by a railway vehicle.

9. An electric motor control system as defined in claim 2, wherein said windings of said motor reversing contactor are controlled by front and back contacts of a pair of electromagnetic relays which are connected to said first and second means and provide memory of the last command signal received from said control circuit.

Claims

1. An electric motor control system for a railway switch machine which shifts the switch points between two extreme positions comprising, a reversible motor, an electromagnetic clutch and a source of electrical power, a control circuit including a normal and a reverse circuit for remotely controlling the energization of said reversible motor and said electromagnetic clutch from said power source, said control circuit having a first means for receiving and storing a first command signal, said first means controlling energization of said electromagnetic clutch and said reversible motor so that said switch points are shifted from one to the other extreme position, said control circuit having a second means for receiving and storing a second command signal, said second means controlling the energization of said electromagnetic clutch and said reversible motor so that the switch points are shifted from the other to the one extreme position, said electromagnetic clutch is arranged to slip when the trailing action opposes the shifting of the switch points by the energization of the reversible motor so that no damage will occur to the railway switch, a cut-out switch common to said first and second means for disabling said normal and reverse circuits thereby preventing energization of said reversible motor and said electromagnetic clutch, and an overload device for sensing the amount of current flowing through said reversible motor and for interrupting both said first and second means which causes said reversible motor to be deenergized when an abnormal amount of current flows through said reversible motor.